1. Field of the Invention
The present invention relates to a method of treating a surface of a rotating wafer for carrying out various surface treatment such as etching, cleaning of the surface of the wafer, and formation of films on the surface of the wafer by supplying a gas for surface treatment such as etching and cleaning and a gas for forming films and the like to the surface of various wafers such as a semiconductor wafer while rotating the wafers in a horizontal plane, and, more particularly, to a technique for enhancing uniformity of surface treatment of a wafer over the whole surface of the wafer in a manufacturing process of a semiconductor device.
2. Description of the Related Art
It is possible to carry out surface treatment of a wafer such as a semiconductor wafer by supplying gases for various surface treatment over the whole surface of the wafer while rotating the wafer in a horizontal plane. Thus, etching and cleaning of the surface of a wafer and formation of films on the surface of the wafer, for example, are carried out. So far, a technique disclosed in Japanese Patent Laying-Open No. 62-165925 (1987) has been used as a method for carrying out treatment uniformly in the whole area of the surface of the wafer to be treated. The laid open application discloses a diffusion plate having openings of various shapes for supplying a gas uniformly to the surface of the wafer. Specifically, according to the laid open application, the diffusion plate is arranged opposite the wafer to be treated, spaced a predetermined distance apart from the wafer. A surface treating gas is supplied uniformly toward the surface of the wafer through openings of various shapes formed in the diffusion plate.
Furthermore, there is a technique in which a diffusion plate is provided a part of the diffusion plate for discharging a surface treating gas is rotated or a wafer under treatment is rotated by rotating a table for carrying the wafer. In these techniques, the optimum condition for carrying out uniform treatment was found out by trial-and-error, and surface treatment was carried out in accordance with that condition.
In the conventional methods, however, the condition for carrying out uniform surface treatment of a wafer varies depending on the supplied flow rate of a surface treating gas, the exhausting ratio from a surface treatment chamber and the like. Therefore, it was extremely difficult to set a condition of making it possible to carry out surface treatment uniformly over the whole surface of a wafer, and it was especially difficult to numerically represent the condition in the conventional methods.